Pressure = Force/Area. So you have P= 1000 lb/(20 in^2) = 50 pounds/in^2 = 50 psi.

Or in metric units: P = 4500N/129.03 cm^2 = 34.9 N/cm^2. The common unit for pressure in metric units is pascals, which is equivalent to newtons per square meter, so do the conversion like this:

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